1. Field of the Invention
This invention relates to a polymer bead recovery apparatus comprising: a housing comprising a recovery tank having an internal cavity and an exterior surface, the recovery tank having at least one inlet and at least one outlet, the housing further comprising a walkway situated on the exterior surface of the recovery tank, the recovery tank comprising a shaker deck having a plurality of interchangeable screens and being situated above the internal cavity of the recovery tank, and the walkway providing access to the screens, and the recovery tank having a collection vessel under or situated adjacent to the rig shaker screens. More specifically, the present invention relates to a method of recovering polymer beads using a low profile recovery apparatus having an internal cavity, interchangeable screens situated above the cavity, a collection vessel and a circulating system for creating turbulence within the cavity and isolating and then recovering polymer beads from a mixture of solid particulate material, drilling or separating fluids, polymer beads and drilled solids.
2. Description of the Related Art
During the drilling of a well, it is commonplace to process the drilling mud returns to remove undesired drilling cuttings or solids and to recovery polymer beads using shale shakers or the like. The shale shaker has been the primary piece of equipment, which separates the drilling solids from the mud. It is also desired to produce mud with a low drilled solids content. By recycling the large drilled solids in the well bore, smaller sizes of drilled solids are produced and thereby build up the solids content of the mud. As the solids content increases, the mud must be thinned by adding additional water which necessitates the addition of more weighting material to maintain the mud at its desired weight.
In addition to removing undesired drilled solids and producing a mud with a low drilled solids content, it is also desirable to recover and recycle drilling fluid and polymer beads. The polymer beads are usually circulated through the system once or twice and then discarded with the drilled cuttings. It is economically beneficial to recycle these potentially costly fluids and beads during the drilling process. It is conventional to screen mud over a shale shaker having screens ranging in size from 10 to 200 mesh. Therefore, any solid particulate materials having a particle size larger than the shale shaker screen would be removed from the system with the drilled solids.
There have been efforts to deposit drilled solids and polymer beads into a tank containing a liquid with a specific gravity less than the specific gravity of drilled solids but greater than the specific gravity of the polymer beads. As a result, the beads will migrate or float to the top of the tank and the drilled solids will submerge or sink to the bottom of the tank. The beads may then be skimmed from the top of the tank. In these systems, the flotation liquid in the tank requires an aqueous solution of sodium carbonate or any number of soluble salts such as sodium chloride or calcium chloride to induce the separation of beads, liquid and drilled solids. The introduction of the more efficient shale shakers that produce finer solids has made this flotation system ineffective. This flotation system did not anticipate the problem of fine solids building up in the separating fluid zone. As these solids continue to build up, the separating liquid becomes extremely viscous or thick and will not allow the beads to be effectively separated from the drilled cuttings or solids. Furthermore, the sodium carbonates on the surface of the beads, which are returned to the drilling fluid, create a problem for the drilling fluid known as carbonate contamination. Carbonate contamination produces carbonic acid, which reacts with the alkaline products in the drilling fluid, which in turn reduces the effectiveness of the drilling fluid thinners such as lignosulfonates and allow the drilling fluids to become increasingly thick and unacceptable.
There are also complicated systems, which at minimum, requires a shale shaker, a recovery tank with a hydrocyclone manifold system and a recovery shaker. In such systems, the shale shaker is mounted several feet above the recovery tank. These systems require to be completely shut down before any changes or modification can be made during the recovery process, such as any adjustments in screen sizes, clogging, safety issues involving the adjustments, etc. The amount of equipment and space necessary to use this system also hinders the broad use of the product. These complicated systems do not teach or suggest an apparatus having interchangeable screens and a walkway to provide the user with access to the screens for safe and easy changes and adjustments. Furthermore, the system of the present invention further provides for a transfer vessel and a portable recovery apparatus that can be situated at any desired location, as opposed to having to be located adjacent to or below the shale shaker. The apparatus of the present invention relates to a low profile design that provides the user with mobility and portability in the field of polymer bead recovery technology.
The system and apparatus of the present invention does not require a bulky shale shaker and removes the large solid particulate materials and drilled solids before the mixture enters the recovery tank, which is usually the main cause of clogging in the recovery tank and requires stopping the recovery process to fix the clogging. Besides the time and money lost during the stoppage, the exercise of cleaning the clogs in the recovery tank has become a major injury and safety hazard.